The Iowa Scaled Engineering SimpleSig Crossover Detector is a Modular Signaling System (MSS)-compliant current-based block detector for model railroad layout modules. It is a complete “crossover” unit - block detection for a module without signals - as described in the Modular Signal System (MSS) standard.  It is intended for use on modules that require block detection to participate in layouts where MSS signaling is in use, but the module itself does not have signals.

 It integrates our highly-reliable ATOM DCC current block detector, a rugged and reliable MSS bus interface, and plug-and-play MSS RJ45 connections into one simple.  Plus, it works with a wide variety of power sources - DC, AC, or DCC - so it can be connected directly into the Free-mo accessory power bus.  Simply connect power, run one leg of track power through the current sense transformer, plug the MSS bus in both ends, and your module is ready to participate in an MSS-signalled setup!

Features

• Fully compliant with the Modular Signal System 1.x, 2.x, and proposed 3.x standards.
• Highly sensitive (1mA, or ~10k ohms) yet resistant to false detection
  
• Single button sensitivity adjustment if needed (no fiddling with tiny potentiometers!)
• Accepts 5V to 24V of AC, DC, or DCC for power
  
• Rugged and reliable "goof-proof" MSS bus drivers
  
• Easy installation with connectors and terminal blocks
• 0.4s turn on and 2.5s turn off delay to eliminate glitching
  
• Onboard power and detection indicator LEDs
• Isolated MSS driver to prevent ground loops
  

Specifications

Size: 2.9"(L) x 1.5"(W)
Power: 5-24V power (AC, DC, or DCC) at 20mA (max)
Sensitivity:  1mA standard, adjustable up to 11mA.

Many thanks to Gregg Fuhriman and other contributors for the development and release of the Modular Signal System specification.

Documents

The complete Kicad design files are available on GitHub.

User Manual

Schematic